Heat oven to 350°F. Grease and flour a 9 x 13-inch cake pan. Pour applesauce into 2-cup liquid measuring cup. Add enough water to bring mixture to 2 cups. Stir cinnamon into applesauce mixture. Prepare combined cake mixes according to package directions, substituting applesauce mixture for liquid in recipe. Pour batter into prepared pan; bake until cake is golden brown and a toothpick inserted in center comes out clean, 50 to 60 minutes. Transfer to wire rack, and let cool 15 minutes. Invert cake and cool completely.
Spoon 1 cup vanilla frosting and all of chocolate frosting into separate resealable plastic bags. Snip small corner off each bag. Tint remaining vanilla frosting golden yellow by using several drops yellow food coloring and one drop red.
Place cake on clean work surface. Cut cake crosswise, 4 inches from short end of cake. Separate pieces. Trim 1 inch off each short edge of smaller cake piece to make hood of bus.
Place large rectangle, cut edge down, on serving platter with flat side (bottom of cake) facing you. For front of bus, spread flat side with yellow frosting. Press hood piece onto front center of frosted cake. Spread remaining yellow frosting over entire cake.
For windows, pipe rectangles on front and back of bus with white vanilla frosting. Spread lightly with spatula to smooth. Trim chocolate licorice to frame windows and to make front grille. Shape chocolate bars into two bumpers, four squares for headlights and taillights, and four rectangles with one rounded edge each for flashers. Place on front and back of cake.
Using chocolate frosting, pipe lines around edges of cake. Write "school bus" on front at top. Pipe dots of vanilla frosting onto chocolate pieces; attach red M&M's as flashing lights and white mints as headlights. Fold fruit leather in half over toothpick, and cut into octagon. Pipe border around edges of octagon and "stop" in center. Attach to "driver's" side of cake with toothpick.
Trim 1/2 inch from one edge of each doughnut, and press along each side of cake for wheels. Attach red licorice lace as steering wheel. If desired, attach whole vanilla wafers for people in bus, and decorate faces with tube frosting. Sprinkle ground vanilla wafers around front, back, and sides of cake to make dirt road, and green-colored coconut along sides of road for grass, if using.